Thermold is an aftermarket manufacturer of magazines for several types of popular modern firearms. This particular magazine is designed to work in conjunction with AR-15 platform rifles chambered in the popular .223 Remington/5.56mm NATO. The magazine is made from a durable Zytel Nylon which resists heat, dirt, and rust. These dent resistant magazines are self lubricating and non-corrosive due to their unique design.